ethereum.homestead.utils.message

 1"""
 2Hardfork Utility Functions For The Message Data-structure
 3^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 4
 5.. contents:: Table of Contents
 6    :backlinks: none
 7    :local:
 8
 9Introduction
10------------
11
12Message specific functions used in this homestead version of specification.
13"""
14from typing import Optional, Union
15
16from ethereum.base_types import U256, Bytes, Bytes0, Uint
17
18from ..fork_types import Address
19from ..state import get_account
20from ..vm import Environment, Message
21from .address import compute_contract_address
22
23
24def prepare_message(
25    caller: Address,
26    target: Union[Bytes0, Address],
27    value: U256,
28    data: Bytes,
29    gas: Uint,
30    env: Environment,
31    code_address: Optional[Address] = None,
32    should_transfer_value: bool = True,
33) -> Message:
34    """
35    Execute a transaction against the provided environment.
36
37    Parameters
38    ----------
39    caller :
40        Address which initiated the transaction
41    target :
42        Address whose code will be executed
43    value :
44        Value to be transferred.
45    data :
46        Array of bytes provided to the code in `target`.
47    gas :
48        Gas provided for the code in `target`.
49    env :
50        Environment for the Ethereum Virtual Machine.
51    code_address :
52        This is usually same as the `target` address except when an alternative
53        accounts code needs to be executed.
54        eg. `CALLCODE` calling a precompile.
55    should_transfer_value :
56        if True ETH should be transferred while executing a message call.
57
58    Returns
59    -------
60    message: `ethereum.homestead.vm.Message`
61        Items containing contract creation or message call specific data.
62    """
63    if isinstance(target, Bytes0):
64        current_target = compute_contract_address(
65            caller,
66            get_account(env.state, caller).nonce - U256(1),
67        )
68        msg_data = Bytes(b"")
69        code = data
70    elif isinstance(target, Address):
71        current_target = target
72        msg_data = data
73        code = get_account(env.state, target).code
74        if code_address is None:
75            code_address = target
76    else:
77        raise AssertionError("Target must be address or empty bytes")
78
79    return Message(
80        caller=caller,
81        target=target,
82        gas=gas,
83        value=value,
84        data=msg_data,
85        code=code,
86        depth=Uint(0),
87        current_target=current_target,
88        code_address=code_address,
89        should_transfer_value=should_transfer_value,
90        parent_evm=None,
91    )